src.it.unimi.dsi.fastutil.io.InspectableFileCachedInputStream Maven / Gradle / Ivy
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package it.unimi.dsi.fastutil.io;
/*
* Copyright (C) 2005-2015 Sebastiano Vigna
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import it.unimi.dsi.fastutil.bytes.ByteArrays;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.FileChannel;
import java.nio.channels.WritableByteChannel;
/** A {@linkplain RepositionableStream repositionable} {@link MeasurableInputStream} based on
* cached data received by a {@link WritableByteChannel} whose first bytes can be inspected directly.
*
* An instance of this class acts as a buffer holding the bytes written through its
* {@link WritableByteChannel} interface (which can be easily turned into an {@link OutputStream} using
* {@link Channels#newOutputStream(WritableByteChannel)}). The data can be discarded at any time using
* {@link #clear()}. The first {@link #inspectable} bytes of {@link #buffer} contains the first
* bytes written. When {@link #buffer} is full, the bytes are written to an overflow
* file.
*
*
At any time, the stream of bytes written since creation (or since the last {@link #clear()})
* are available as a fully implemented {@link MeasurableInputStream} which also implements
* {@link RepositionableStream} and {@linkplain #mark(int) supports marking}.
* Note that you must arbitrate carefully write and read accesses,
* as it is always possible to call {@link #write(ByteBuffer)}
* and thus modify the {@linkplain #length() length} of the {@link MeasurableInputStream}.
*
*
The method {@link #close()} makes the {@link MeasurableInputStream} and {@link WritableByteChannel} state-changing methods temporarily throw an {@link IOException}, but
* does not otherwise modify the state of the stream. You can {@linkplain #reopen() reopen} the stream
* later, or {@linkplain #clear() clear} it.
* The method {@link #dispose()} can be used to release
* the resources associated with the stream.
*
*
Buffering
*
* This class provides no form of buffering except for the memory buffer described above, both
* when reading and when writing. Users should consider wrapping instances of this class with a
* {@link FastBufferedInputStream}, as reads after the buffer has been exhausted will be performed
* directly on a {@link RandomAccessFile}. */
public class InspectableFileCachedInputStream extends MeasurableInputStream implements RepositionableStream, WritableByteChannel {
public static final boolean DEBUG = false;
/** The default buffer size (64KiB). */
public static final int DEFAULT_BUFFER_SIZE = 64 * 1024;
/** The inspection buffer. The first {@link #inspectable} bytes contain the first part of the input stream.
* The buffer is available for inspection, but users should not modify its content. */
public final byte[] buffer;
/** The number of valid bytes currently in {@link #buffer}. */
public int inspectable;
/** The overflow file used by this stream: it is created at construction time, and deleted on {@link #close()}. */
private final File overflowFile;
/** The random access file used to access the overflow file. */
private final RandomAccessFile randomAccessFile;
/** {@link #randomAccessFile randomAccessFile#getChannel()}, cached. */
private final FileChannel fileChannel;
/** The position on this stream (i.e., the index of the next byte to be returned). */
private long position;
/** The {@linkplain #mark(int) mark}, if set, or -1. */
private long mark;
/** The write position of the {@link #randomAccessFile overflow file}. When {@link #inspectable} is equal
* to {@link #buffer buffer.length}, the length of the stream is {@link #inspectable} + {@link #writePosition}. */
private long writePosition;
/** Creates a new instance with specified buffer size and overlow-file directory.
*
* @param bufferSize the buffer size, in bytes.
* @param overflowFile the directory where the overflow file should be created, or null for the default temporary directory.
*/
public InspectableFileCachedInputStream( final int bufferSize, final File overflowFile ) throws IOException {
if ( bufferSize <= 0 ) throw new IllegalArgumentException( "Illegal buffer size " + bufferSize );
if ( overflowFile != null ) this.overflowFile = overflowFile;
else ( this.overflowFile = File.createTempFile( getClass().getSimpleName(), "overflow" ) ).deleteOnExit();
buffer = new byte[ bufferSize ];
randomAccessFile = new RandomAccessFile( this.overflowFile, "rw" );
fileChannel = randomAccessFile.getChannel();
mark = -1;
}
/** Creates a new instance with specified buffer size and default overflow-file directory.
*
* @param bufferSize the buffer size, in bytes.
*/
public InspectableFileCachedInputStream( final int bufferSize ) throws IOException {
this( bufferSize, null );
}
/** Creates a new instance with default buffer size and overflow-file directory. */
public InspectableFileCachedInputStream() throws IOException {
this( DEFAULT_BUFFER_SIZE );
}
private void ensureOpen() throws IOException {
if ( position == -1 ) throw new IOException( "This " + getClass().getSimpleName() + " is closed" );
}
/** Clears the content of this {@link InspectableFileCachedInputStream}, zeroing the length of the represented
* stream. */
public void clear() throws IOException {
if ( ! fileChannel.isOpen() ) throw new IOException( "This " + getClass().getSimpleName() + " is closed" );
writePosition = position = inspectable = 0;
mark = -1;
}
/** Appends the content of a specified buffer to the end of the currently represented stream.
*
* @param byteBuffer a byte buffer.
* @return the number of bytes appended (i.e., {@link ByteBuffer#remaining() byteBuffer.remaining()}).
*/
public int write( final ByteBuffer byteBuffer ) throws IOException {
ensureOpen();
final int remaining = byteBuffer.remaining();
if ( inspectable < buffer.length ) {
// Still some space in the inspectable buffer.
final int toBuffer = Math.min( buffer.length - inspectable, remaining );
byteBuffer.get( buffer, inspectable, toBuffer );
inspectable += toBuffer;
}
if ( byteBuffer.hasRemaining() ) {
fileChannel.position( writePosition );
writePosition += fileChannel.write( byteBuffer );
}
return remaining;
}
/** Truncates the overflow file to a given size if possible.
*
* @param size the new size; the final size is the maximum between the current write position (i.e., the length
* of the represented stream minus the length of the inspection buffer) and this value.
*/
public void truncate( final long size ) throws FileNotFoundException, IOException {
fileChannel.truncate( Math.max( size, writePosition ) );
}
/** Makes the stream unreadable until the next {@link #clear()}.
*
* @see #reopen()
*/
@Override
public void close() {
position = -1;
}
/** Makes the stream readable again after a {@link #close()}.
*
* @see #close()
*/
public void reopen() throws IOException {
if ( ! fileChannel.isOpen() ) throw new IOException( "This " + getClass().getSimpleName() + " is closed" );
position = 0;
}
/** Disposes this stream, deleting the overflow file. After that, the stream is unusable. */
public void dispose() throws IOException {
position = -1;
randomAccessFile.close();
overflowFile.delete();
}
protected void finalize() throws Throwable {
try {
dispose();
}
finally {
super.finalize();
}
}
@Override
public int available() throws IOException {
ensureOpen();
return (int)Math.min( Integer.MAX_VALUE, length() - position );
}
@Override
public int read( byte[] b, int offset, int length ) throws IOException {
ensureOpen();
if ( length == 0 ) return 0;
if ( position == length() ) return -1; // Nothing to read.
ByteArrays.ensureOffsetLength( b, offset, length );
int read = 0;
if ( position < inspectable ) {
/* The first min(inspectable - readPosition, length) bytes should be taken from the buffer. */
final int toCopy = Math.min( inspectable - (int)position, length );
System.arraycopy( buffer, (int)position, b, offset, toCopy );
length -= toCopy;
offset += toCopy;
position += toCopy;
read = toCopy;
}
if ( length > 0 ) { // We want to read more.
if ( position == length() ) return read != 0 ? read : -1; // There's nothing more to read.
fileChannel.position( position - inspectable );
final int toRead = (int)Math.min( length() - position, length );
// This is *intentionally* not a readFully(). Let the language to its stuff.
final int t = randomAccessFile.read( b, offset, toRead );
position += t;
read += t;
}
return read;
}
@Override
public int read( byte[] b ) throws IOException {
return read( b, 0, b.length );
}
@Override
public long skip( final long n ) throws IOException {
ensureOpen();
final long toSkip = Math.min( n, length() - position );
position += toSkip;
return toSkip;
}
@Override
public int read() throws IOException {
ensureOpen();
if ( position == length() ) return -1; // Nothing to read
if ( position < inspectable ) return buffer[ (int)position++ ] & 0xFF;
fileChannel.position( position - inspectable );
position++;
return randomAccessFile.read();
}
@Override
public long length() throws IOException {
ensureOpen();
return inspectable + writePosition;
}
@Override
public long position() throws IOException {
ensureOpen();
return position;
}
/** Positions the input stream.
*
* @param position the new position (will be minimized with {@link #length()}).
*/
public void position( final long position ) throws IOException {
this.position = Math.min( position, length() );
}
@Override
public boolean isOpen() {
return position != -1;
}
@Override
public void mark( final int readlimit ) {
mark = position;
}
@Override
public void reset() throws IOException {
ensureOpen();
if ( mark == -1 ) throw new IOException( "Mark has not been set" );
position( mark );
}
@Override
public boolean markSupported() {
return true;
}
}